帮我写个android的登陆注册，使用sqlite数据库

好的，以下是一个简单的Android登陆注册应用示例，使用SQLite数据库：

1. 创建一个名为“LoginRegistration”的Android项目。
2. 在res/layout目录下创建两个布局文件：activity_login.xml和activity_register.xml，分别用于登录和注册页面的UI设计。
3. 在res/menu目录下创建一个menu.xml文件，用于添加菜单项。
4. 在AndroidManifest.xml文件中添加以下权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

5. 创建一个名为“DatabaseHelper”的Java类，用于创建和管理SQLite数据库。

public class DatabaseHelper extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "LoginRegistration.db";
    public static final String TABLE_NAME = "user_table";
    public static final String COL_1 = "ID";
    public static final String COL_2 = "USERNAME";
    public static final String COL_3 = "PASSWORD";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, USERNAME TEXT, PASSWORD TEXT)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }

    public boolean insertData(String username, String password) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL_2, username);
        contentValues.put(COL_3, password);
        long result = db.insert(TABLE_NAME, null, contentValues);
        return result != -1;
    }

    public boolean checkUser(String username, String password) {
        SQLiteDatabase db = this.getWritableDatabase();
        String[] columns = { COL_1 };
        String selection = COL_2 + " = ?" + " AND " + COL_3 + " = ?";
        String[] selectionArgs = { username, password };
        Cursor cursor = db.query(TABLE_NAME, columns, selection, selectionArgs, null, null, null);
        int count = cursor.getCount();
        cursor.close();
        return count > 0;
    }
}

6. 在LoginActivity中实现登录功能。在onCreate方法中，获取用户名和密码输入框的实例，并设置登录按钮的点击事件：

public class LoginActivity extends AppCompatActivity {
    EditText usernameEditText, passwordEditText;
    Button loginButton;
    DatabaseHelper databaseHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        usernameEditText = findViewById(R.id.usernameEditText);
        passwordEditText = findViewById(R.id.passwordEditText);
        loginButton = findViewById(R.id.loginButton);
        databaseHelper = new DatabaseHelper(this);

        loginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String username = usernameEditText.getText().toString();
                String password = passwordEditText.getText().toString();

                if (databaseHelper.checkUser(username, password)) {
                    Toast.makeText(LoginActivity.this, "Login successful", Toast.LENGTH_SHORT).show();
                    Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                    startActivity(intent);
                } else {
                    Toast.makeText(LoginActivity.this, "Invalid username or password", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

7. 在RegisterActivity中实现注册功能。在onCreate方法中，获取用户名、密码和确认密码输入框的实例，并设置注册按钮的点击事件：

public class RegisterActivity extends AppCompatActivity {
    EditText usernameEditText, passwordEditText, confirmPasswordEditText;
    Button registerButton;
    DatabaseHelper databaseHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);

        usernameEditText = findViewById(R.id.usernameEditText);
        passwordEditText = findViewById(R.id.passwordEditText);
        confirmPasswordEditText = findViewById(R.id.confirmPasswordEditText);
        registerButton = findViewById(R.id.registerButton);
        databaseHelper = new DatabaseHelper(this);

        registerButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String username = usernameEditText.getText().toString();
                String password = passwordEditText.getText().toString();
                String confirmPassword = confirmPasswordEditText.getText().toString();

                if (password.equals(confirmPassword)) {
                    boolean isInserted = databaseHelper.insertData(username, password);
                    if (isInserted) {
                        Toast.makeText(RegisterActivity.this, "Registration successful", Toast.LENGTH_SHORT).show();
                        Intent intent = new Intent(RegisterActivity.this, LoginActivity.class);
                        startActivity(intent);
                    } else {
                        Toast.makeText(RegisterActivity.this, "Registration failed", Toast.LENGTH_SHORT).show();
                    }
                } else {
                    Toast.makeText(RegisterActivity.this, "Passwords do not match", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

8. 在MainActivity中添加菜单项，用于退出应用：

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.exit:
                finish();
                System.exit(0);
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

9. 运行应用，测试登录和注册功能。

以上是一个简单的Android登陆注册应用示例，使用SQLite数据库。